Concordance and Relative Performance of the 2023 ACR/EULAR and Revised Sapporo Criteria in Antiphospholipid Syndrome and Analysis of Risk Factors for Recurrent Thrombosis: A Single-Center Cohort Study

Background and Objectives: To evaluate the concordance and relative performance of the 2023 American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) classification criteria compared with the revised Sapporo (2006) criteria and to identify potential risk factors for recurrent thrombosis among patients classified as antiphospholipid syndrome (APS) according to the 2023 criteria. Materials and Methods: This retrospective cohort study included 82 patients with documented antiphospholipid antibody (aPL) positivity between October 2022 and August 2024. The revised Sapporo criteria were used as the comparator classification system to evaluate the concordance and relative performance of the 2023 ACR/EULAR criteria. Secondary analyses were restricted to patients fulfilling the 2023 criteria (n = 55), in whom clinical characteristics and potential risk factors for recurrent thrombosis were evaluated. Results: Of the 82 aPL-positive patients, 9 fulfilled only the revised Sapporo criteria, 1 fulfilled only the 2023 criteria, 54 met both criteria sets, and 18 met neither. Using the revised Sapporo criteria as the comparator, the 2023 criteria demonstrated a relative sensitivity of 85.7% and relative specificity of 95.0%. Positive and negative agreement rates were 98.2% and 66.7%, respectively. Among patients classified as APS according to the 2023 criteria, disease duration was significantly longer in patients with recurrent thrombosis in univariate analysis (p = 0.028); however, this association did not remain significant after multivariable adjustment. Conclusions: The 2023 ACR/EULAR criteria demonstrated higher relative specificity but lower relative sensitivity compared with the revised Sapporo criteria. No independent predictor of recurrent thrombosis was identified after multivariable adjustment, although the limited number of outcome events may have reduced statistical power. However, most recurrent thrombotic events occurred in patients with subtherapeutic INR levels, suggesting the importance of careful anticoagulation management in patients with APS.